Well i think the reward should be that in the next ranked game you get a free dodge during champ select, and you can continue to dodge until you get into a ranked game.
Another reward i was thinking about is you can also select your pick order. If more than 1 players on a team had S or S+ from previous game the game randomly select whom to have pick order selection.
Yeah, couldnt that be a good idea?
How about a free dog?